A fish-eye lens is known as a lens having a wide-angle field of view or visual field. A proposal has been made for an omnidirectional camera system for monitoring a predetermined region with the use of this fish-eye lens. Such an omnidirectional camera system generally has functions such as panning, tilting, zooming (i.e., pan, tilt, zoom) and rotation (or rolling or roll). In recent years, a proposal has also been made for an omnidirectional camera system which, as compared with the conventional mechanical pan, tilt or zoom mode, electrically processes input side image data captured by the fish-eye lens, thereby fulfilling various functions, such as pan, tilt, zoom and rotation, and eliminating the distortion of the image, without moving the apparatus.
FIG. 14 is a block diagram of this type of omnidirectional camera system according to the conventional technology. As shown in this drawing, a CMOS image sensor 1, which is an imaging means, forms image data as an electrical signal based on a wide-angle image captured by a fish-eye lens 2. This image data is an electrical digital signal having a distortion component remaining as such when captured by the fish-eye lens 2. This signal is subjected to predetermined color processing at a color processing unit 3, whereby it is written into a frame memory 4 as input side image data DI having color information as well as luminance or brightness information.
A parameter setting device 5, on the other hand, has settings of parameters concerned with pan, tilt, zoom and rotation for cutting out a region to be displayed, in the image captured by the fish-eye lens 2, and parameters related to the center and radius of the fish-eye lens 2. That is, the parameter setting device 5 functions as an input/output device for these parameters. The parameters about the pan, tilt and rotation are set as angular information, the parameter about the zoom is set as magnification information, and the parameters about the center and radius of the fish-eye lens 2 are set as positional information and numerical information. A geometrical position calculation device 6 calculates the geometrical position of each pixel in the input side image data DI, which corresponds to each pixel on a display screen (output screen) 9a of a display device 9, in order to correct the distortion, by the fish-eye lens 2, of the image in the region to be cut out as output based on the parameters set in the parameter setting device 5.
An output side image data generation unit 7 forms output side image data DO corrected for the distortion based on the geometrical position of each pixel in the input side image data DI calculated by the geometrical position calculation device 6, and the input side image data DI stored in the frame memory 4. This output side image data DO is data obtained by sequentially combining brightness information, etc. based on the input side image data DI for each pixel on the output screen corresponding to the geometrical position. The output side image data DO is sequentially stored into a buffer memory 8, pixel by pixel, and is reproduced on the display screen (output screen) 9a of the display device 9 frame by frame. In this manner, the image in the predetermined cut-out region and corrected for distortion is reproduced on the display screen 9a. 
As a publication which discloses a technology of the same type as that of the above-described conventional technology, the following patent document 1 is existent:
Patent Document 1: JP-A-2000-83242
With the above-described omnidirectional camera system, the input side image data DI, which is the output signal of the image sensor 1 as the imaging means, is written into the frame memory 4. After the writing of the input side image data DI corresponding to one frame is completed, the output side image data DO is formed by reference to the contents of storage in the frame memory 4. Thus, during such a series of processing steps, a time lag occurs. Such a time lag manifests itself as a display delay on the display screen 9a. 
The present invention has been accomplished in the light of the above-described conventional technologies. It is an object of the invention to provide a camera system capable of achieving a series of processings, without using a frame memory, in the conversion of input side image data into output side image data, which involves predetermined processing of a geometrical position, such as correction of distortion of the input side image data.